Maredia, A. | bioRxiv Science

bioRxiv2025

μCT-based, Three-Dimensional Cortical Bone Mineral Density Distribution reveals Unique Phenotypes related to Bone Material Properties.

Bone strength is an important factor for determining fracture risk that is dependent on bone mass and bone architecture as well as bone material properties. Bone material properties are defined, in part, by the heterogeneity and degree of bone mineralization, parameters that can be assessed with a bone mineral density distribution (BMDD) from 2D-histological sections of bone using backscatter electron microscopy (BSEM). Here we perform a comprehensive examination of a 3D-CT-based BMDD to assess its utility in bone research. Analysis of cortical bone CT scans from preclinical studies using anabolic treatments, pro-resorptive conditions, and genetically heterogeneous mouse lines extend and confirm published findings from BSEM-based BMDD. Principal Component Analysis identified features of the BMDD (e.g. skewness, variance, mean degree of mineralized bone or MDMB) that are distinct from the traditional bone phenotyping measures of bone mineral density, bone mineral content, and cortical bone thickness. In addition, BMDD parameters (e.g. MDMB) correlated to indices of bone material properties from Reference Point Indentation (RPI, US 1st, stiffness) and 4-point bending (toughness). These BMDD parameters also increased the predictive value of a multiple linear regression model for US 1st from RPI (from r2=0.26 for traditional bone phenotypes to r2=0.41 for the full model). Thus, CT-based BMDD reveals unique phenotypes related to bone material properties that complement existing bone phenotyping tools thereby increasing our ability to draw biological inferences about the nature of bone and the processes controlling bone mineralization.

physiology↗

bioRxiv2020

Identification of Aorta-Specific DNA Methylation Patterns in Cell-Free DNA from Patients with Bicuspid Aortic Valve-Associated Aortopathy and Correlation with Aortic Wall Cell Death

ObjectiveIn a proof-of-concept study we sought to identify aorta-specific differentially methylated regions (DMRs) detectable in plasma cell-free DNA (cfDNA) obtained from patients with bicuspid aortic valve (BAV)-associated aortopathy. MethodsWe used bioinformatics and publicly-available human methylomes to identify aorta-specific DMRs. We used data from 4D-flow cardiac magnetic resonance imaging to identify regions of elevated aortic wall shear stress (WSS) in patients with BAV-associated aortopathy undergoing surgery and correlated WSS regions with aortic tissue cell death assessed using TUNEL staining. Cell-free DNA was isolated from patient plasma and levels of candidate DMRs were correlated with aortic diameter and aortic wall cell death. ResultsAortic wall cell death was not associated with maximal aortic diameter but was significantly associated with elevated WSS. We identified 24 candidate aorta-specific DMRs and selected 4 for further study. A DMR on chromosome 11 showed acceptable specificity for the aorta and correlated significantly with aortic wall cell death. Plasma levels of total and aorta-specific cfDNA did not correlate with aortic diameter. ConclusionsElevated WSS created by abnormal flow hemodynamics is associated with increased aortic wall cell death which supports the use of aorta-specific cfDNA as a potential tool to identify aortopathy and stratify patient risk. Date and Number of Institutional Review Board ApprovalREB17-0207

molecular biology↗